Nuclear magnetic resonance has been shown to be a useful, non-perturbative tool for studying model membrane systems. However, application to biological membranes has been limited by the broad line widths (short spin-spin relaxation times) and, for certain nuclei, long aquisition times (long spin-lattice relaxation times) which are found for these systems. In these respects biological membranes are similar to solids and methods which have been developed for solid state NMR can be used to study intact biological membranes. 31P NMR will be used to study the role of lipids in various aspects of membrane function. 15N NMR will be used to study the molecular events contributing to protein activity in biological membranes.